function jieliu(fn, time) { 
    let prev = Date.now()     
    return function() {        
     let now = Date.now()        
     if (now - prev > time) {          
      fn()        
      prev = Date.now()       
     }     
    }    
   }    
   function handle() {      
    console.log(Math.random())   
   }
   window.addEventListener('scroll', jieliu(handle, 1000))